Last week's announcement by Apple that the UK launch of the iPad will be delayed by a month was the headline news for consumers, but for geeks a more significant development came on Thursday with some changes in the 21,000-word "agreement" that you have to sign if you are going to develop applications for Apple's iDevices.

Section 3.3.1 of the document stipulates that "Applications must be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS WebKit engine, and only code written in C, C++ and Objective-C may compile and directly link against the documented APIs (eg, applications that link to documented APIs through an intermediary translation or compatibility layer or tool are prohibited)."

Incomprehensible, eh? An API is an application programming interface – ie the protocol that programmers must follow if their software is to work with the iDevice. The really interesting clause, though, is the one enclosed in brackets. Translated into English it reads: screw you, Adobe!

Some background may help here. Adobe makes a lot of influential software – the Photoshop image-processing program, for example; and Acrobat, the program that enables people to create and read PDF files. Adobe also sells Flash, a multimedia platform that has become the de facto standard way to add animation and interactivity to web pages; currently about three-quarters of all online video material is encoded in Flash format.

When the iPhone launched, many consumers were puzzled by the fact that it wouldn't play Flash video. When pressed about this, Steve Jobs claimed testily that the rationale was technical: Flash was "buggy" and allegedly the most common cause of crashes in Apple's Safari browser; and it hogs processor time. If true, these would be reasonable objections: operational stability is far more important for a phone than it is for a PC; and processor power on phones is pretty limited.

Naturally, Adobe disputed the slurs on its product, but – on the (plausible) assumption that Steve Jobs wasn't going to change his mind – set about devising a workaround. On Monday, Shantanu Narayen, Adobe's CEO, launched the latest (fifth) version of the company's Creative Suite – its toolbox for creating multimedia products. "The Adobe CS5", burbled Narayen, "is a phenomenal release which enables you, our customers, to create without boundaries while speeding the creative process from concept to execution. In addition to providing great design tools we also focused on helping you to achieve maximum impact by reaching the broadest number of customers possible." Tucked away in CS5 is a new tool, a Packager for iPhone, which is effectively a program for converting Flash applications into something that will run on the iPhone.

Which is precisely what Apple set out to exclude four days later. The Adobe Packager is what Apple calls "an intermediary translation or compatibility layer or tool". It'd be tempting to see this as just petty vindictiveness, but in fact it's a declaration of war. Steve Jobs sees Flash's near-dominance in the online animation and interactivity sphere as a strategic threat. If Flash continues to spread, then, in the end, Apple will find itself at the mercy of Adobe's development priorities and strategy. And Steve Jobs didn't get where he is today by being dependent on anyone.

There's a lot at stake here, and it's not at all clear how things will pan out. In one scenario, Apple's rebuff of Adobe's new tool will be seen as hubristic folly. As one expert, Dominique Jodoin, put it: "1.2 billion mobile phones are Flash-capable; 70% of online gaming sites run Flash; 98% of internet-enabled desktops use it; 85% of top 100 websites use Flash; it's the No 1 platform for video on the web – 75% of all videos use Flash (including Hulu, Disney and YouTube); 2-3 million person Flash developers community; 90% of creative professionals have Adobe software on their desktops. With numbers and penetration rates like that, the better question is, why wouldn't I choose to support this technology?"

On the other hand, Jean-Louis Gassée (a former Apple executive) proposes a simple thought-experiment: "By the end of 2010, there will be more than 100 million iPhone OS devices (iPod Touch, iPhone, iPad). You're the webmeister at an important content site. The boss comes in and asks you why you're not supporting the iPhone OS devices. 'Our stuff is all Flash-based, chief, those guys don't run Flash'. You're about to become the ex-webmeister. The boss, a really patient sort, asks you to 'think different' about all these 'noncompliant' customers, each of whom has an iTunes account backed by a credit card, and has developed the habit (encouraged by Apple) of paying for content. So, one more time, with feeling: what's your answer?"